Electric discharge device



Dec. 14, 1948. l J, A, WA|NWR|GHT 2,456,474

ELECTRIC DISCHARGE DEVICE Filed July 2, 1946 Figi.

Joseph A Wanrght,

bg vHis Attorneg.

flected dierent amounts Patented Dec. 14, 1948 UNITED STATES r .ortica2,456,474 ELECTRIC DISCHARGE DEVICE Joseph A. Wainwright, Syracuse,

to General Electric Company, a

New York N. Y., assigner corporation oi Application July 2, 1946, SerialN0. 680,895 7 Claims. (Ci. 25d-157) 'contains negative ions inappreciable quantities which tend to form a black spot on thefluorescent screen of the tube. It is also known that particles havingdiierent charge-to-mass ratios are deby a magnetic neld but aresubstantially uniformly deected by an electric field. Cathode ray tubeshave been provided with means for selectively deflecting the electronsand ions by means of suitable electric and magnetic fields. Inaccordance with an important aspect of my present invention I provide anew andimproved discharge device of the beam type in which the ions areremoved from the beam by the selective deiiecton of the ions andelectrons.

It is an object of my invention to provide a new and improved electricdischarge device of the beam type.

It is another object of my invention to provide improved beam delectingmeans for an electric discharge device of the beam type whichselectively deilects the ions and electrons in the beam.

It is a still further object of my invention to vprovide a new andimproved structure for providing a transverse magnetic field forcontrolling the beam of an electric discharge device.

Further objects and advantages of my invention wil1 become apparent asthe following description proceeds, reference being had to theaccompanying drawing, and its scope will be pointed out in the appendedclaims. In the drawing, Fig. 1 is an elevational view, partly insection, of a cathode ray tube embodying my invention; Fig. 2 is anenlarged sectional view of a portion of the device illustrated in Fig. 1and showing in detail the electron gun structure, and Fig. 3 is asectional view taken along the line 3-3 of Fig. 2.

Referring now to the drawing, I have shown my invention as applied to acathode ray tube which may be of the type employed in televisionreceivers, and which includes an envelope I formed of glass. Theenvelope may be of the usual shape including an elongated neck portionand an enlarged or bulbous portion closed at its outer end to provide aviewing window of the tube. The inner surface of the window is providedwith a uorescent coating 2 which may be applied in accordance withtechniques well understood in for devices oi!` the art and which may toadvantage include what are commonly known as medium persistentphosphors. The gun structure is adjacent the neck portion of theenvelope and is supported from the end wall by a plurality of conductors3 which are sealed through the envelope wall. The gun in'- ciudes agenerally cylindrical cathode d supported centrally within a grid member5 which is in the form of an inverted metallic cup having an aperture 6in alinement with the emitting surface of the cathode. As illustrated,the cathode is supported within the grid cylinder 6 on an insulatingdisk 1 and is positioned and retained by suitable spacing and retainingwashers 8, 9 and IIB.-

The grid 5 is supported on a. flanged collar II which is in turn securedto the supporting conductors 3. In accordance with usual electron gunconstruction, a plurality of glass supports or stalks I 2 are secured tothe grid cylinder 5 by laterally projecting metal lugs I3. A second oraccelerating grid cylinder It and an anode cylinder I5 are supported inaxial alinement with the grid cylinder 5 and in spaced and insulatedrelation with respect thereto by a plurality of lugs I6 which are sealedinto the supporting stalks I2. As illustrated, the outer end of theanode cylinder I5 is closed by a disklike member I1, the outer edge ofwhich is spaced slightly from the wall of the envelope and which isprovided ywith a centrally located limiting aperture I8 which confinesthe electron beam projected from the gun. The outer edge of the gun isphysically positioned in the central portion of the neck by a pluralityof spring ngers I9 which extend along the envelope Wall and contact theinterior conducting coating 2t which is applied to the inner wall of theenvelope from the central portion of the neck to within approximatelyone inch of the fluorescent screen 2. The conducting coating may beformed of a graphite solution in accordance with well known practices,and serves as a return conducting path for electrons liberated from theiluorescent screen 2.

As illustrated in the drawing, the outer end of the grid cylinder It andthe inner end of the anode cylinder I5 are positioned in mutually spacedand insulated relation and shaped to define a gap extending at an acuteangle with respect to the longitudinal axis of the gun. Since the anodecylinder I5 operates at a high positive potential with respect to thegrid cylinder It, it will be apparent that'the electric field existingacross `the gap will deflect the electrons of the beam to the left, asviewed in Fig. 2.

The various parts'of the electrongun'are elec- I trically connectedextending radially and 3 with terminal prongs 2i' carried by aninsulating base 2|' by suitable lead-in conductors 22. The base issecured to the end of the neck portion oi' the envelope by a. body ofcement 23. An anode or high voltage terminal 24 is provided on the sidewall of the bulbous portion of the envelope I and a conductor 25 sealedthrough the envelope wall connects the terminal with the internalconducting coating 20. An exterior coating 26 of conducting material maybe applied to the outside of the envelope and in cooperation with theinternal coating 20 provides a capacitive anode connection.

In accordance with an important aspect of my invention, I provide animproved structure for providing a pair of transverse magnetic iields onopposite sides of the gap between cylinders Il and I deflection providedby the electrostatic field across the gap between grid Il and anode I5eil'ect the selective deflection of the electrons and ions of theelectron beam. As illustrated in the drawing, a pair of permanentlymagnetized spring rings 21 and 28 are positioned on the neck of theenvelope on opposite sides of the gap between the accelerating gridcylinder I4 and the anode cylinder I5. These rings may to advantage beformed of one 'of the copper-nickle-iron alloys which'provides a magnetof light weight and high coercive force. The rings are resilient and areeasily mounted on the neck of the tube. As illustrated, the rings 21 and28 are split and mounted on a resilient support which in the illustratedembodiment takes the form of a rubber tube 29 surrounding the neck ofthe envelope. With this construction, it is possible to adjust theangular positions of the rings to provide the desired control of thebeam. The rings 21 and 28 are magnetized in such a manner that a northpole exists at a restricted circumferential portion of the ring providedat a diametrically opposite region. The rings 21 and 28 are furtherpositioned or displaced rotationally 180; that is, the north pole of onemagnet occupies the same radial plane as the south pole of the othermagnet.

In order to assist in the drawing, each pole guiar member having one arm30 extending longitudinally of the gun structure and the other armsecured to the outer wall of the accelerating grid by a suitable tab 3iwhich is welded to the pole piece and to the grid cylinder. Sincerotation of the ring 21 displaces the poles thereof with respect to thepole pieces' it changes the strength of the eld acting on the electronbeam. By independent rotation of rings 21 and 28 the desired trapping ofthe ions is effected and the beam of electrons is directed to thedesired spot on the screen.

The manner in which the electric field produced between the adjacentends of cylinders I3 and il and the magnetic elds produced by thepermanent magnets 21 and 28 operate to deiiect the electron beam and toseparate the electrons and ions will be more apparent from aconsideration of the following description of the operation of thedevice. As will be readily appreciated, the accelerating grid cylinder I4 is operated at a positive potential with respect to the grid cylinder5 and the anode cylinder i5 has a positive and which in comunction withthe and a south pole is positioned on the neck ection of the 4 potentialwith respect to the grid cylinder Il. Electrons emitted from the activesurface of the cathode 4 pass through the aperture 6 of the control gridand through the aperture of the accelerating grid into the regionbeneath the pole pieces 30. .The permanent magnet ring 21 is of theenvelope with the north pole opposite the pole pieceshown in Fig. 2;that is, the pole piece at the back of the electron gun. In other words,the magnetic field lines oi.' force project from the plane of the paperin a direction perpendicular to the axis of the electron gun. With themagnetic field in this direction, the electrons' and ions of the beamare deflected to the right, as viewed in Fig 2. As stated earlier in thespecification, the deilection oi.' the charged particles in the magneticeld is dependent upon the charge-to-mass ratios of these particles sothat the ions of the beam are deflected substantially less than theelectrons of Fig. 2. The deheavy ions at this point is substantially thesame as the deection of the electrons, but since the ions weresubstantially undefiected by the magnetic ileld,` they are now directedto the left of the axis of the electron gun and are collected on thewall of the anode cylinder I 5, The electrons are deected to the leftthe center of the anode cylinder and pass through the limiting apertureI8 at the outer end of the anode cylinder. The effect of the electricand magnetic fields has been decribed above as ifthey were actingindepend ently, actually the electrons and ions are deected inaccordance with the resultant effect of these two eids. The secondpermanent magnet ring 28 is mounted with the north pole on the top ofthe envelope, as viewed in Figs. 1 and 2, and is eective to deilect theelectrons to the n right. The use of the second magnet ring, which ispreferably much weaker than the magnet ring 21 provides an adiustmentfor bringing the electron beam exactly into the center of the anodecylinder I5. It is apparent the angular position of the ring 28independently of the ring 21 that the iinal position of the electronbeam may be controlled. It'is also apparent that certain structuralfeatures of the magnet structure may be employed for purposes other thanas components of an ion trap.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that changesand modications may be made without departing from I of the beam typeincluding an envelope, a source of electrons including an electron gunpositioned at one end of said envelope, means including said gun forproducing a beam of electrons and sub- Jecting said beam to anelectrostatic field having a component transverse to the axis of saidbeam, and means for subjecting said beam to a transverse magnetic fieldto deflect the electrons of i said beam in a direction opposite to thedeection produced by said electrostatic field, said last mentioned meansincluding a substantially comthat by adjusting plete ring of permanentlymagnetized to produce a ux in the direction of a diameter of said ringresiliently supported on the exterior of said envelope.

2. Incombination, an electric discharge device of the beam typeincluding an envelope, a source of electrons including an electron gunpositioned at one end of said envelope, means including said gun forproducing a beam of electrons, and means for subjecting said beam to atransverse magnetic field to deflect the electrons of said beam in adirection transverse to the axis of said beam, said last mentioned meansincluding a substantially complete ring of permanently magnetized andmechanically resilient` material supported on the exterior of saidenvelope.

3. In combination, an electric discharge device including an envelopehaving an elongated neck portion, an electron gun structure supportedwithin said envelope for producing an electron beam, and means forcontrolling the transverse .position of said beam including apermanently magnetized substantially complete spring ring supported onthe exterior of said neck portion and rotatably and axially adjustableto control the magnitude and direction of the deflection oi said beamproduced by said means.

4. In combination, an electric discharge device including an envelopehaving an elongated neck portion, and electron gun structure supportedwithin said envelope for producing an electron beam, a layer ofresilient material surrounding said neck portion, and means forcontrolling the transverse position of said beam including a permanentlymagnetized substantially complete spring ring supported on said materialand adjustable in position relative to said material to control themagnitudeand direction of the deflection of said beam produced by saidmeans.

5. In combination, an electric discharge device of the beam typeincluding an envelope having a neck portion, an electron gun supportedin said neck portion and includingadjacent conducting members supportedin spaced insulated relation and adapted when energized by potentials ofdifferent magnitudes to subject the electrons of said beam to atransverse electric field. and permanently magnetized ringlike memberssupported on the neck portion of said envelope in axially spacedrelation on opposite 'sides of the space between said conductingmembers.

6. In combination, an electric discharge device of the beam typeincluding an envelope having a neck portion, an electron gun supportedin said magnetized material neck portion and including adjacentconducting members supported in spaced insulated relation and adaptedwhen energized by potentials of diierent magnitudes to subject theelectrons of the beam to a transverse electric iield, a pair ofring-like members of permanently magnetized material supported inaxially spaced relation on the neck portion of said discharge device,said rings extending substantially completely around said neck portionand being magnetized to produce a flux along a diameter of the rings,and means for supporting said rings permitting rotational adjustment ofone of said rings relative to the other, the resultant action of saidrings and the electric field produced by said members cooperating toseparate the ions and electrons of the beam.

'7. An electric discharge device of the beam type including an envelopehaving aneck portion, an electron gun supported in the neck por tion ofsaid envelope providing an electron beam, said gun structure includinggenerally cylindrical grid and anode electrodes supported in mutuallyspaced end-to-end relation, the adjacent ends of said electrodesdefining a gap therebetween extending at an acute angle with respect tothe axis of said beam, a pair of ring-like permanent magnets supportedon said neck portion at points spaced along said beam and on oppositesides ofsaid gap, said magnets being similarly magnetized androtationally displaced degrees to provide transverse magnetic fields oflopposite polarity on opposite sides of said gap and cooperating with theelectric field produced' across said gap to selectively deiiect theelectrons and ions of said beam and to cause the collection of the ionson said anode electrode.

JOSEPH A. WAINRIGHT.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,188,579 Schlesinger Jan. 20,1940 2,211,613 Bowie Aug. 13, 1940 2,274,586 Branson Feb. 24, 1942FOREIGN PATENTS Number Country Date 464,637 Great Britain Apr. 21, 1937498,491 Great Britain Jan. 9, 1939 518,221 Great Britain Feb. 21, 1940

